V4L/DVB (13949): Move a dereference below a NULL test

If the NULL test is necessary, then the dereference should be moved below
the NULL test.

The semantic patch that makes this change is as follows:
(http://www.emn.fr/x-info/coccinelle/)

// <smpl>
@@
type T;
expression E;
identifier i,fld;
statement S;
@@

- T i = E->fld;
+ T i;
  ... when != E
      when != i
  if (E == NULL) S
+ i = E->fld;
// </smpl>
Signed-off-by: Julia Lawall <julia@diku.dk>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/dvb/dvb-usb/dw2102.c

@@ -470,12 +470,13 @@ static int s6x0_i2c_transfer(struct i2c_adapter *adap, struct i2c_msg msg[],
 								int num)
 {
 	struct dvb_usb_device *d = i2c_get_adapdata(adap);
-	struct usb_device *udev = d->udev;
+	struct usb_device *udev;
 	int ret = 0;
 	int len, i, j;
 
 	if (!d)
 		return -ENODEV;
+	udev = d->udev;
 	if (mutex_lock_interruptible(&d->i2c_mutex) < 0)
 		return -EAGAIN;